In mineral mining, it is known to provide a number of control valves in a common block and to actuate the valves selectively with the aid of tappets by partially rotating a part of a composite cam shaft with the aid of a manual lever accessible from outside the block. On release of the lever, the cam shaft part is automatically restored to a neutral non-operative position by a "dead-man's handle" type of restoration system.
U.S. Pat. No. 4,310,027 issued Jan. 12, 1982 and assigned to the same assignee as this application, describes a known device and this patent is herein incorporated by a reference. U.S. patent application Ser. No. 485,243 filed Apr. 15, 1983 and also assigned to the same assignee as the present application also describes another form of device related to the present invention.
A general object of the present invention is to provide an improved form of hydraulic control device.